The invention relates to a process for the cleaning and, respectively, restoring of a packed column with packing elements, the specific gravity of which is lower than the specific gravity of a scrubbing agent. The column is utilized for gas purification by means of a scrubbing operation, wherein obstructions of the packing space by solids formed during the scrubbing step occur, requiring from time to time restoration of the column by flooding.
Packed columns are preferably employed for gas purification, especially the scrubbing of gases, since they offer large gas/liquid exchange surfaces and thus effectively enhance the scrubbing operation. See, e.g., Ullmanns Encyklopaedie der Technischen Chemie 2:591-595 (1972).
In the case of oxidative H.sub.2 S scrubbing operations, for example, elemental sulfur is formed during scrubbing which leads to clogging of the packed column thus making regeneration of the packing charge a necessity. This phenomenon is caused by a variety of formed deposits, and can also occur in other scrubbing operations, for example, metal sulfides or metal carbonyl in methanol scrubbing operations, phosphines in potash scrubbing operations and the like. In Ullmans Encyklopaedie der Technischen Chemie 2:595, 1972, it recommended not to use packed columns in scrubbing operations if a danger of contamination from deposits existed.
For example DOS No. 3,513,809, which corresponds to U.S. Pat. No. 4,687,496, discloses a method of cleaning a packed column utilized in a scrubbing operation, performed with a scrubbing medium, for gas purification, and having been obstructed with deposits. In order to break up these deposits, this method floods, i.e., fills up, the packed column with, for example, scrubbing agent.
By introducing an inert gas into the column filled with scrubbing agent, the floatable packing elements are floatingly stirred up and set into a swirling motion whereby the obstructions are broken up and either drop to the bottom of the vessel from which they can be withdrawn or they are discharged from the column together with the scrubbing agent.
A grave disadvantage of the known method resides in that at lest two parallel-connected scrubbing columns are necessary for the regenerating process in order to operate the scrubbing operation continuously. In this arrangement, gas is scrubbed in one column while the other column, filled with scrubbing medium, is cleaner. The necessity of employing two scrubbing columns has a very negative effect on the costs of the scrubbing process since scrubbing columns are the most expensive parts of a scrubbing operation. The pipelines required on account of the second scrubbing column likewise represent a considerable cost factor.
A further drawback of the known process resides in that a very large amount of scrubbing agent must constantly be made available for cleaning, this scrubbing agent being stored in an additional storage tank. Furthermore, a compressor for introduction of the inert gas is required in order to overcome the pressure gradient resulting from the standing level of the scrubbing medium present in the column during cleaning.